Level 10 Titans are pretty rare. I had one in a mm game a couple weeks ago and was killing another titan, starbase, and a big fleet at the same time (with just my titan). I think it's nice to have a cap so you can feel great when you get to it.

Because capitalships cap at level 10. And because titans don't need to be any more powerful.

Key difference is I can end up having 16 Capital ships yet only 1 Titan. If I max out 8 Cap ships (which would be remarkable), I can still max out 8 more. The likelyhood of that is much smaller IMO. A Titan however once capped leaves nothing....

Anything can always be more powerful.

Level 10 Titans are pretty rare.

Maybe, but if you get one then it is likely the AI will get one as well (they cheat). Now you are both maxed and just increase the chance of a stand off.

I think it's nice to have a cap so you can feel great when you get to it.

Personally I would rather win....

I now have a capped Titan and multiple capped capital ships yet if they were not capped the game would be playable for nearly the same amount of time I already played it. The reason being is all the empires would be racing to anihalate the smaller/mid ones and occasionally laying waste to the greater empires outlieing systems. Instead, because a couple empires are now nearly maxing out it will likely end up being an endless attack and retreat game and racing your fleet around to other locations